UX: tweak location of like count

UX: clean up fade logic so it meshes with new like style
EXTENSIBILITY: add hook for insertion of custom HTML for buttons
UX: stop suppressing share for anon, like expander is not suppressed
 old behavior is inconsistent


also reimplements like count expander as a proper button,
adds a nice label for it

app/assets/stylesheets/mobile/topic-post.scss

@@ -27,20 +27,18 @@ span.badge-posts {
   display: none;
 }
 
-.show-likes {
-  padding-left: 0;
-  padding-right: 0;
-  font-size: inherit;
-  span.badge-posts {color: scale-color($primary, $lightness: 60%);}
-  i {
-    display: none;
-  }
-}
-
 nav.post-controls {
   clear: both;
 }
 
+.who-liked {
+  margin-left: 20px;
+}
+
+button.like-count {
+  padding: 8px 4px;
+}
+
 button {
   border: none;
   font-size: 1.214em;